Memory Requirements

Memory Requirements

The program portion of 177Bug is approximately 512KB of code, consisting of:

Download

Debugger

Diagnostic packages

and is contained entirely in EPROM. The EPROM sockets on the MVME177 are mapped starting at location $FF800000.

177Bug requires a minimum of 64KB of contiguous read/write memory to operate.

The ENV command controls where this block of memory is located. Regardless of where the onboard RAM is located, the first 64KB is used for 177Bug stack and static variable space and the rest is reserved as user space. Whenever the MVME177 is reset:

Target PC is initialized to the address corresponding to the beginning of the user space

Target stack pointers are initialized to addresses within the user space

Target Interrupt Stack Pointer (ISP) set to the top of the user space

At power-up or reset, all 8KB of memory at addresses $FFE0C000 through $FFE0DFFF is completely changed by the 177Bug initial stack.

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Motorola MVME177 manual Memory Requirements